1. Field of the Invention
The invention relates to bioremediation compositions for oil spills and to processes for using those compositions.
2. Description of Related Art
The state of the art for remediation of oil spills in marine and freshwater environments involves use of chemical dispersants. In situ burning and mechanical separation are also extensively used. These methods have advantages and disadvantages. Bioremediation is one of the most promising alternatives to the use of chemical dispersants.
Biodegradation is a natural process, and with enough time, microorganisms can eliminate many components of oil from the environment. Prior art bioremediation approaches for marine and freshwater oil spills fall into three major categories: (1) stimulation of indigenous microorganisms through addition of nutrients (i.e., fertilization); (2) introduction of special assemblages of naturally occurring oil-degrading microorganisms (i.e., seeding); and (3) introduction of genetically engineered microorganisms (GEMs) with special oil-degrading properties. Stimulation of indigenous organisms by the addition of nutrients is the approach that has been tested most rigorously. This approach is viewed by many researchers as the most promising one for responding to most types of marine and freshwater spills.
More development and testing of both fertilization and seeding technologies are needed before on-scene coordinators or others responsible for oil spill cleanup would be comfortable advocating their use. Most decision makers prefer more traditional methods, and usually are not willing to experiment during a real spill. Bioremediation technologies for response to marine and freshwater oil spills, although promising, are still in the experimental phase.
The rate at which petroleum biodegradation occurs is thought to be limited by the rate at which a mousse is formed. A mousse is a water-in-oil emulsion, typically formed after an oil spill when heavy wave action causes water to be entrained in the insoluble components of spilled oil. Factors influencing mousse formation after crude oil spills in salt water environments are well characterized. The formation of a mousse is attributed to the heavy constituents such as wax, resin, and asphaltene.
Several experimental approaches involve the use of natural wax esters. For example, U.S. Pat. No. 5,807,724 describes techniques for “microencapsulating” oil-degrading bacteria in shells of natural beeswax. U.S. Pat. No. 6,699,390 discloses an alternative approach, in which microspheres of natural beeswax are used to encourage indigenous bacterial growth. Unfortunately, the processes of microencapsulation and microsphere manufacture are difficult and require special equipment. Moreover, the mechanism by which natural wax esters act in oil spill remediation is not well characterized.
Another problem lies in the fact that the oil remediation compositions of the prior art are generally formulated to function in a particular set of environmental conditions. If a spill occurs in conditions different from those anticipated, the composition may be less effective or ineffective.